1. Field of the Invention
The present invention relates to mechanisms that hold workpieces in position for welding abutting edges and particularly to a hydraulic jacking device for aligning and welding boiler water wall panels.
2. Description of the Prior Art
Large utility boiler furnace walls are manufactured from tubing welded with membrane between the tubes to form panels which when welded together make a water cooled firebox wall to contain fire. These panels are frequently replaced because of wear, corrosion and fatigue. The panels of tube banks that need replacement are generally cut out using a power saw or a cutting torch. When new panels and old existing panels are required to be fit together, they require jacking with extreme force to make them fit due to the warpage of the old panel
Many devices have been invented and employed to align workpieces that are to be welded together and to support these materials during the welding process. Prior art patents provide aligning clamp devices and welding fixtures or jigs. None of the prior art patents provide a jacking device for boiler water wall tube panels.
Prior art U.S. Pat. No. 4,081,651, Mar. 28, 1978 to Randolph, shows apparatus for supporting and rotating a pair of hollow tank sections of generally circular cross section, including scalene frusto-conical tank sections, during welding of the sections in end-to-end abutting relation to form an elongted tank. The apparatus includes three  longitudinally spaced, axially aligned, rotatable rings which define a welding cage. The center ring includes a plurality of circumferentially spaced, radially directed jacks, each extendible the same distance regardless of the resistance encountered by a particular jack to force the abutting edges of the tank sections into a precise circular cross section and support and hold the abutting edges in aligned relation during rotation and welding. The two side rings include circumferentially spaced radially directed jacks of the seek and find type that will automatically extend until all jacks exert the same force on the tank sections extending from each side of the center ring to thereby support the tank sections for rotation about the common axis of the three rings, regardless of whether the tank sections are of cylindrical, right frusto-conical or scalene frusto-conical shape. A longitudinally extending conveyor is provided which extends within the welding cage and on either side of the welding cage for moving adjacent tank sections longitudinally toward each other into abutting engagement for welding, and for moving welded sections longitudinally of the cage.
Prior art U.S. Pat. No. 4,475,726, issued Oct. 9, 1984 to Smith, provides a rugged sturdy workpiece positioning mechanism that effectively and efficiently positions and holds at least two workpieces for further operations. The mechanism includes a main support that is slidably connected to a first workpiece and a housing assembly, which is affixed to the main support and extends above and engages the second workpiece. The housing assembly includes two side plates, a cam with a handle rotatably attached to the sideplates, a ratchet to lock the cam into a fixed position and a load bearing surface actuated by the cam and slidably received between the side plates. The edge of the cam  abuts the load-bearing member. When the cam is rotated in a predetermined direction, the distance between its axis of rotation and the load bearing member increases driving the load bearing member downward. The load-bearing surface engages the workpiece and forces the second workpiece into a desired position relative to the first workpiece. Once the joining operation is completed, the mechanism is slidably detached from the workpieces.
Prior art U.S. Pat. No. 5,542,177 issued Aug. 6, 1996 and U.S. Pat. No. 5,356,248 issued Oct. 18, 1994 both to Mark W. Hillestad, show a method and apparatus for repairing boiler tube walls by cutting out and replacing a worn or damaged section thereof involving the use of a power tool having a rotary milling head specially adapted to remove membrane material from between tube ends which are exposed when the damaged section is removed and optionally to simultaneously bevel the end of a tube as membrane material is being removed. The method and apparatus of the invention allows for the rapid and precise removal of membrane material from between the exposed tube ends to facilitate subsequent beveling and welding operations or for concurrent beveling and membrane removal, while substantially reducing the risk of weakening or damaging the tube wall by avoiding excess removal of material therefrom.
Prior art U.S. Pat. No. 4,739,688 issued Apr. 26, 1988 and U.S. Pat. No. 4,830,551 issued May 16, 1989 and U.S. Pat. No. 5,044,075 issued Sep. 3, 1991 all to Matthew T. Brennan and James A. Moruzzi, provide boiler tube repair apparatus including elongated guide rail structure for securing to a boiler tube panel adjacent a desired cut region, and three tool assemblies for mounting on the guide rail structure. Each tool assembly includes carriage structure with guide  structure for engaging the guide rail structure and support structure on which a tube machining tool is mounted and that defines a tool movement axis dedicated to and coordinated with that tool. Each machining tool includes a drive motor, a manual motor control, a drive shaft and a machining member such as a cutter disc or head.
Prior art U.S. Pat. No. 5,511,717, issued Apr. 30, 1996 to Uusitalo, concerns a device for aligning the edges of plate-like bodies for welding the edges together. The device comprises a plate-like support member to be inserted into a gap between the edges to be welded, and support means positioned on the opposite sides of the plates and arranged to press the edges of the bodies to be welded into the same plane.
Prior art U.S. Pat. No. 3,182,988, issued May 11, 1965 to Woodall, claims a welding fixture or jig whereby two steel plates or the like may be disposed in a fixed relationship to one another to permit welding of the plates together. The welding fixture is seated upon lugs that are welded to the plates. Wedges are provided which engage the holding lugs to urge the plates into alignment. A large passageway is provided in the fixture for welding access to the abutting edges of the two steel plates.
Prior art U.S. Pat. No. 2,101,856, issued Dec. 14, 1937 to Hines, discloses a welding apparatus that comprises a plate apertured to receive apertured holding lugs on members to be welded together. The apparatus also comprises wedges adapted to be driven through the apertures in the holding lugs to draw the members against the plate. The apparatus further comprises a shoulder on the plate adjacent to an aperture in it and a wedge adapted to be driven between a holding lug and the shoulder to shift the member laterally with respect to the plate. 
Prior art U.S. Pat. No. 2,306,032, issued Dec. 22, 1942 to Baumgard, puts forth a coupling apparatus for butt-welding sheet metal structures. The device comprises a bridging member that extends across the adjacent edges of the members to be welded. The bridging member has apertures for receiving apertured lugs attached to the sheet metal structures. The device further comprises wedges for engaging slots in the bridge member and the lugs, which causes the sheet metal structures to become aligned.
Prior art U.S. Pat. No. 2,469,965, issued May 10, 1949 to Holt, indicates an aligning clamp for holding plate material to be welded along adjoining edges. The clamp comprises an elongated strap member, which is set on edge transversely across the gap between the plates and matches the curve of said plates. U-shaped members are welded to the plates and straddle the elongated strap. Tapered tension pins are wedged between the closed end of the U-shaped members and the elongated strap, thereby causing the plate members to align with one another.
What is needed is a hydraulic jack system for the power required to align boiler water tube panels.